Investigation of the conversion mechanism for hydrogen production by coal gasification in supercritical water

The technology of supercritical water gasification (SCWG) of coal has a great prospect because it converts coal into hydrogen-rich gas products efficiently and cleanly. However, there are bottlenecks affecting the complete gasification of coal in supercritical water (SCW) without catalyst under moderate conditions. This work is to explore the restricted factor for complete gasification of coal in SCW by investigating the conversion mechanism. The conversion mechanism of SCWG of coal with and without K2CO3 is proposed. Poly cyclic aromatic hydrocarbons (PAHs) with graphite phase structures are formed by the condensation of aromatic structures at 550-750 degrees C. It is the restricted factor due to its characteristic of difficulty to be gasified. There is no condensation of aromatic structures in the process of SCWG of coal with K2CO3, which effectively inhibited the formation of PAHs with graphite phase structures. K2CO3 dramatically promoted the SCWG of coal, leading to carbon gasification efficiency (CE) reaching 98.43%. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the conversion mechanism of coal in supercritical water and finds that the addition of K2CO3 can significantly promote the process of supercritical water gasification, leading to higher carbon gasification efficiency.